問題文
The extended forms of the encapsulation that carries circuits across the core and of the one that joins many points at the second layer are written on a port. Which identifiers of VLANs may be used with them, and what does the extended form that carries circuits ask of the two ends?
選択肢
- Every identifier from zero upward may be used, the value zero being as good as any other for a circuit, and that form asks the identifier of the port taking traffic in to match the identifier of the port letting it out
- Every identifier from one upward may be used, the value zero being held back for tagging the priority of a frame, and that form asks the identifier of the port taking traffic in to match the identifier of the port letting it out
- Every identifier from one upward may be used, the value zero being held back for tagging the priority of a frame, and that form asks the identifier of the port taking traffic in to differ from the identifier of the port letting it out
- Every identifier from zero upward may be used, the value zero being as good as any other for a circuit, and that form asks the identifier of the port taking traffic in to differ from the identifier of the port letting it out